At least 54 people were killed and 88 others wounded in clashes at a prison in Venezuela's northwestern city of Barquisimeto, a hospital director who was at the scene has said.

Most of those injured at the Uribana prison in Lara state late on Friday suffered gunshot wounds, Ruy Medina, the hospital official said.

Among the dead are a pastor and a member of the National Guard - the rest are said to be inmates, the hospital director said.

He called the death toll "alarming", saying it was based solely on bodies brought to the hospital.

Saying that "prisons need to be places of re-education not for crimes and mafia", Nicholas Maduro, Venezuelan vice president, said an "immediate investigation" has been launched into the circumstances surrounding the deaths.

Medina said the inmates began arriving at the hospital shortly before midday, and that 14 of the injured had wounds severe enough to require surgery.

Iris Varela, the government minister responsible for Venezuela's jails and prisons, said the riot was set off after inmates rebelled when prison authorities launched a sweep of the facility in search of illicit weapons.

Varela had said earlier in the day that there was an "undetermined number" of casualties from the melee.

The state of Venezuelan prisons have often been called into question, especially for their overcrowding, which is among the worst in Latin America.